Re: Boeing landing procedures

From:         ehahn@bass.mitre.org (Ed Hahn)
Organization: The MITRE Corporation, McLean, Va.
Date:         27 Apr 95 03:00:25 
References:   1 2
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>   In article <airliners.1995.437@ohare.Chicago.COM> "Steven J. Leighton" <ak95@solo.pipex.com> writes:

<snip>

   >I have been led to believe that for the final 200 feet before
   >touchdown Boeing aircraft use the INS system for landing as opposed
   >to ILS alone. Could someone please clarify if this is truly the case.

One detail that people seem to forget is that the Inertial Reference
System (IRS) provides _attitude_ information, and thus is an integral
part of any flight maneuver, ILS landings included.  In this
application, the position/speed information is a backup for radio
navigation.  (Although if the ILS signals were lost, the aircraft
could not continue the approach unless the runway was in sight.)

(BTW - FMS equipped aircraft have an IRS, not an INS.  The FMS
performs the navigation function, while the IRUs provide
position/velocity/attitude information.  Older aircraft without FMCs
have the navigation function integrated with the
position/velocity/attitude function, hence INS.)

Nickpicky, I know...

ed

--------   Ed Hahn | ehahn@mitre.org | (703) 883-5988   --------
The above comment reflects the opinions of the author, and does not
constitute endorsement or implied warranty by the MITRE Corporation.
Really, I wouldn't kid you about a thing like this.